Dr Richard Haass flies out of Belfast tomorrow after a week-long series of engagements that included 30 meetings with politicians, academics, clergy, the Loyal Orders, business leaders and senior civil servants.

He said: "We come away from this week with a strong sense of possibility about what can and what should be accomplished."

Dr Haass, who was envoy to Northern Ireland during George Bush's presidency in 2001-03, was appointed to chair the new political talks initiative aimed at resolving three of the most contentious issues facing the power sharing institutions at Stormont.

Supported by US foreign affairs expert Dr Meghan O'Sullivan, he has until Christmas to find common ground on three outstanding issues not dealt with by the 1998 Good Friday peace agreement - flags and emblems; parades; and dealing with the legacy of the past.

He said: "This is not our first rodeo, we have both been in a number of political processes formal and informal in the Middle East, Asia, Latin America and here (Northern Ireland). Based upon that experience and the quality of the conversations and also our familiarity with the issues I believe there is a real chance to succeed.

"But, that is just that - a real chance is not a guarantee. Obviously it depends upon the willingness of some people to make some tough decisions and then defend them."

The tone and substance of meetings which culminated in a plenary session with the five Executive parties were described as encouraging.

But, the former diplomat who faces a tight deadline to produce recommendations on the way forward, also claimed more time would not necessarily mean more progress.

"We have made clear all along that we are working under a deadline, that we will finish our work before December 31 of this year," he said. "Nothing that I have heard or read leads me to think that more time will result in more progress. If that were the case I would consider it.

"It is obvious that the critical variable in our work here is not time nor is it me personally or Meghan O'Sullivan but rather the willingness and the ability of the political leaders in Northern Ireland to make difficult choices and to make the case for those choices to and with the people who live here."

Meanwhile, Professor O'Sullivan said although no side had thrown down a gauntlet dealing with the legacy of the past could prove to be the biggest sticking point.

She said: "The past seems to be in a different category. It is much more nebulous, it has to address a much wider range of issues and there are so many different models that can be approached that have been used in Northern Ireland and other parts of the world.

"We feel good about the prospects for progress on each of the three fronts but the past is the one that will be the hardest for us to get our arms around."

When Dr Haass returns in late October he is expected to hold meetings in London and Dublin. He will also take his team to other areas of Northern Ireland during November.

"For this round and the next round the thrust of what we are doing is listening and asking and then come November and December the nature of the interaction will change," he said.

"Our entire purpose here is to produce a set of proposals or principles that will be broadly acceptable."

While the focus of most meetings was on the three key issues the talks also touched on the economy, education and housing issues. More than 100 online submissions have been made.

Dr Haass has acknowledged that a troubled summer in Northern Ireland, when simmering community tensions boiled over into street disorder on a number of occasions, was indicative of the urgency around finding an agreed way forward.

His departure tomorrow coincides with a major loyalist parade through the commercial heart of Belfast. Up to 5,000 people and 20 bands are expected to march through the city centre as part of a protest organised by a group calling itself Loyalist Peace Protesters. They will make their way to north Belfast where Orangemen have set up a "protest camp" close to a sectarian flashpoint.

Last month there were violent scenes on Royal Avenue - Belfast's main shopping street - after a loyalist parade was stopped by police.